using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;

namespace Hello_World
{
    /// <summary>
    /// This is the main type for your game
    /// </summary>
    public class Game1 : Microsoft.Xna.Framework.Game
    {
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;
        Texture2D backgroundTexture;
        float scrollPosition = 0;

        public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";
        }

        /// <summary>
        /// Allows the game to perform any initialization it needs to before starting to run.
        /// This is where it can query for any required services and load any non-graphic
        /// related content.  Calling base.Initialize will enumerate through any components
        /// and initialize them as well.
        /// </summary>
        protected override void Initialize()
        {
            // TODO: Add your initialization logic here
            backgroundTexture = Content.Load<Texture2D>("CityGroundSmall");
            base.Initialize();
        }

        /// <summary>
        /// LoadContent will be called once per game and is the place to load
        /// all of your content.
        /// </summary>
        protected override void LoadContent()
        {
            // Create a new SpriteBatch, which can be used to draw textures.
            spriteBatch = new SpriteBatch(GraphicsDevice);

            // TODO: use this.Content to load your game content here
        }

        /// <summary>
        /// UnloadContent will be called once per game and is the place to unload
        /// all content.
        /// </summary>
        protected override void UnloadContent()
        {
            // TODO: Unload any non ContentManager content here
        }

        /// <summary>
        /// Allows the game to run logic such as updating the world,
        /// checking for collisions, gathering input, and playing audio.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Update(GameTime gameTime)
        {
            // Allows the game to exit
            GamePadState gamePad = GamePad.GetState(PlayerIndex.One);
            KeyboardState keyboard = Keyboard.GetState();
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed || keyboard.IsKeyDown(Keys.Escape))
                this.Exit();
            float moveFactorPerSecond = 400*(float) gameTime.ElapsedGameTime.TotalMilliseconds/1000.0f;
            if (gamePad.DPad.Up == ButtonState.Pressed || keyboard.IsKeyDown(Keys.Up))
                scrollPosition += moveFactorPerSecond;
            if (gamePad.DPad.Down == ButtonState.Pressed || keyboard.IsKeyDown(Keys.Down))
                scrollPosition -= moveFactorPerSecond;
            base.Update(gameTime);
        }

        /// <summary>
        /// This is called when the game should draw itself.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.Green);

            // TODO: Add your drawing code here
            spriteBatch.Begin();
            int resolutionWidth = graphics.GraphicsDevice.Viewport.Width;
            int resolutionHeight = graphics.GraphicsDevice.Viewport.Height;
            for (int x = 0; x <= resolutionWidth / backgroundTexture.Width; x++)
            {
                for (int y = -1; y <= resolutionHeight / backgroundTexture.Height + 1; y++)
                {
                    Vector2 position = new Vector2(x * backgroundTexture.Width, y * backgroundTexture.Height + ((int)scrollPosition) %   backgroundTexture.Height);
                    spriteBatch.Draw(backgroundTexture, position, Color.White);
                }
            }
            spriteBatch.End();
            base.Draw(gameTime);
        }
    }
}
